As an image forming method to obtain a high quality toner image via high speed image formation, there is a method of forming an image through the steps of developing an electrostatic latent image on an electrostatic latent image carrier with toner supplied by a developing roller; and transferring a formed toner image onto a transfer material such as a paper sheet and the like via a member such as an intermediate transfer member.
Excellent toner transferability from an electrostatic latent image carrier to an intermediate transfer member, and further from the intermediate transfer member to a transfer material, and also a cleaning performance to clean the remaining toner after transferring are desired for the intermediate transfer member employed in this image forming method.
In order to obtain the excellent toner transferability from an intermediate transfer member to a transfer material, disclosed is a technique of controlling resistance by containing a conductive material such as carbon black in an intermediate transfer member (refer to Patent Document 1, for example).
Also disclosed is a technique of controlling resistance of the intermediate transfer member surface by containing a conductive agent providing electron conductivity onto a surface layer of the intermediate transfer member (refer to Patent Document 1, for example).
In the case of a number of prints printed employing this intermediate transfer member, the secondary transfer performance concerning a transferring process from an intermediate transfer member to a transfer material is to be degraded.
In order to avoid degradation of secondary transfer performance, it is tried to introduce a surface potential detecting device installed in an image forming apparatus (refer to Patent Document 2, for example).
This is a method in which a surface potential detecting device to detect the potential on the back surface of the intermediate transfer member at a point between the primary transfer position and the secondary transfer position is provided in order to solve the problem concerning the degradation of the secondary transfer performance.
However, there was a problem such that the method of installing a surface potential detecting device in an image forming apparatus led could cost a lot more.
In order to provide an intermediate transfer member exhibiting both the excellent first and second transfer ability, together with excellent durability, it is tried to utilize polyurethane used for a member composed of the surface brought into contact with toner (surface layer), (refer to Patent Document 3, for example).
As for the above-described polyurethane, the constitution polyol is polyolefin based polyol, and the foregoing polyol is one in which dimmer acid based polyol having a hydroxyl group terminal is blended, or not blended
Also disclosed is an image forming apparatus exhibiting excellent secondary transferability, fitted with an intermediate transfer member capable of avoiding generation of image defects such as text image hollow defects and the like (refer to Patent Document 4, for example).
It is specifically reported that a material having the surface of low surface energy is obtained by combining a resin material exhibiting an excellent mechanical characteristic with low surface energy powder and a conductive agent and further dispersing them, and the resulting material is employed as an intermediate transfer member to accomplish the foregoing statement.
(Patent Document 1) Japanese Patent O.P.I. Publication No. 2001-242725
(Patent Document 2) Japanese Patent O.P.I. Publication No. 2002-365937
(Patent Document 3) Japanese Patent O.P.I. Publication No. 2002-311720
(Patent Document 4) Japanese Patent O.P.I. Publication No. 11-231684
However, an intermediate transfer member with polyurethane, or an intermediate transfer member obtained by combining a resin material exhibiting an excellent mechanical characteristic with low surface energy powder and a conductive agent and further dispersing them was not capable of acquiring excellent secondary transferability continuously with no rapture even though it was repeatedly used.